openfoodnetwork/app/webpacker/controllers/flash_controller.js

import { Controller } from "stimulus";

document.addEventListener("turbolinks:before-cache", () =>
  document.getElementById("flash").remove()
);

export default class extends Controller {
  connect() {
    setTimeout(this.fadeout.bind(this), 3000);
  }

  fadeout() {
    this.element.classList.add("animate-hide-500");
    setTimeout(this.close.bind(this), 500);
  }

  close() {
    this.element.remove();
  }
}